Keldysh field theory for nonequilibrium condensation in a parametrically pumped polariton system

We develop a quantum field theory for parametrically pumped polaritons using Keldysh Green's function techniques. By considering the mean-field and Gaussian fluctuations, we find that the low energy physics of the highly non-equilibrium phase transition to the optical parametric oscillator regime is in many ways similar to equilibrium condensation. In particular, we show that this phase transition can be associated with an effective chemical potential, at which the system's bosonic distribution function diverges, and an effective temperature. As in equilibrium systems, the transition is achieved by tuning this effective chemical potential to the energy of the lowest normal mode. Since the occupations of the modes are available, we determine experimentally observable properties, such as the luminescence and absorption spectra.Comment: 16 pages, 14 figure

Petri Net Modelling for Enhanced IT Asset Recycling Solutions

From preliminary design through product sustainment to end of life removal, optimal performance through the entire life cycle, is one of the most important design considerations in engineering systems. There are a number of mathematical modelling techniques available to determine the performance of any system, or process, design. This paper focuses on the Petri Net technique for the representation and simulation of complex cases with the ultimate aim of automatically generating a model from the system, or process, description. If the model can be automatically generated changes can be investigated easily, enabling different designs to be investigated. Within this research, a Petri Net model is developed for a process of recycling IT assets. This model is simulated and programmed in Matlab©. The model enables the simulation of various flow paths through the recycling process, giving an understanding of the current process limiting factors. These can then be used to identify possible ways of improving the efficiency of the recycling process and enhancing the current IT asset management strategy. The future aim of this research is the automatic generation of a system model for complex industrial systems and processes by converting the SysML – based specifications into Petri Nets

Reliability Modelling of Automated Guided Vehicles by the Use of Failure Modes Effects and Criticality Analysis, and Fault Tree Analysis

Automated Guided Vehicles (AGVs) are being increasingly used for intelligent transportation and distribution of materials in warehouses and auto-production lines. In this paper, a preliminary hazard analysis of an AGV\u27s critical components is conducted by the approach of Failure Modes Effects and Criticality Analysis (FMECA). To implement this research, a particular AGV transport system is modelled as a phased mission. Then, Fault Tree Analysis (FTA) is adopted to model the causes of phase failure, enabling the probability of success in each phase and hence mission success to be determined. Through this research, a promising technical approach is established, which allows the identification of the critical AGV components and crucial mission phases of AGVs at the design stage

Optimising police dispatch for incident response in real-time

It is crucial that police forces operate in a cost efficient manner and, in the case of incident response, that the most efficient resources are allocated. The current procedure is that police response units are allocated manually by a dispatcher using a resource list and mapping software. The efficiency of this process can be improved by the use of integrated mathematical approaches embedded within an automatic framework, yielding the optimal selection framework developed in this paper. The framework combines mapping and routing algorithms, and a decision process to facilitate optimal officer selection for incident response. The decision process considers information such as quickest response time, predicted traffic conditions, driving qualifications, response unit availability and demand coverage. The selection framework has been tested and validated through simulation and has shown to increase the efficiency of response units through reduced response times, increased response unit availability, and greater demand coverage

Plant species or flower colour diversity? Identifying the drivers of public and invertebrate response to designed annual meadows

© 2018 The Authors There is increasing evidence of the benefits of introducing urban meadows as an alternative to amenity mown grass in public greenspaces, both for biodiversity, and human wellbeing. Developing a better understanding of the meadow characteristics driving human and wildlife response is therefore critical. We addressed this by assessing public and invertebrate response to eight different annual meadow mixes defined by two levels of plant species diversity and two levels of colour diversity, sown in an urban park in Luton, UK, in April 2015. On-site questionnaires with the visiting public were conducted in July, August and September 2015. Invertebrate responses were assessed via contemporaneous visual surveys and one sweep net survey (August 2015). Flower colour diversity had effects on human aesthetic response and the response of pollinators such as bumblebees and hoverflies. Plant species diversity, however, was not a driver of human response with evidence that people used colour diversity as a cue to assessing species diversity. Plant species diversity did affect some invertebrates, with higher abundances of certain taxa in low species diversity meadows. Our findings indicate that if the priority for sown meadows is to maximise human aesthetic enjoyment and the abundance and diversity of observable invertebrates, particularly pollinators, managers of urban green infrastructure should prioritise high flower colour diversity mixes over those of high plant species diversity. Incorporating late-flowering non-native species such as Coreopsis tinctoria (plains coreopsis) can prolong the attractiveness of the meadows for people and availability of resources for pollinators and would therefore be beneficial

Lickometry: A novel and sensitive method for assessing functional deficits in rats after stroke

The need for sensitive, easy to administer assessments of long-term functional deficits is crucial in pre-clinical stroke research. In the present study, we introduce lickometry (lick microstructure analysis) as a precise method to assess sensorimotor deficits up to 40 days after middle cerebral artery occlusion in rats. Impairments in drinking efficiency compared to controls, and a compensatory increase in the number of drinking clusters were observed. This highlights the utility of this easy to administer task in assessing subtle, long-term deficits, which could be likened to oral deficits in patients

Automated guided vehicle mission reliability modelling using a combined fault tree and Petri net approach

Automated guided vehicles (AGVs) are being extensively used for intelligent transportation and distribution of materials in warehouses and autoproduction lines due to their attributes of high efficiency and low costs. Such vehicles travel along a predefined route to deliver desired tasks without the supervision of an operator. Much effort in this area has focused primarily on route optimisation and traffic management of these AGVs. However, the health management of these vehicles and their optimal mission configuration have received little attention. To assure their added value, taking a typical AGV transport system as an example, the capability to evaluate reliability issues in AGVs are investigated in this paper. Following a failure modes effects and criticality analysis (FMECA), the reliability of the AGV system is analysed via fault tree analysis (FTA) and the vehicles mission reliability is evaluated using the Petri net (PN) method. By performing the analysis, the acceptability of failure of the mission can be analysed, and hence the service capability and potential profit of the AGV system can be reviewed and the mission altered where performance is unacceptable. The PN method could easily be extended to have the capability to deal with fleet AGV mission reliability assessment

Human pluripotent stem cell-derived striatal interneurons: differentiation and maturation in vitro and in the rat brain

Striatal interneurons are born in the medial and caudal ganglionic eminences (MGE and CGE) and play an important role in human striatal function and dysfunction in Huntington's disease and dystonia. MGE/CGE-like neural progenitors have been generated from human pluripotent stem cells (hPSCs) for studying cortical interneuron development and cell therapy for epilepsy and other neurodevelopmental disorders. Here, we report the capacity of hPSC-derived MGE/CGE-like progenitors to differentiate into functional striatal interneurons. In vitro, these hPSC neuronal derivatives expressed cortical and striatal interneuron markers at the mRNA and protein level and displayed maturing electrophysiological properties. Following transplantation into neonatal rat striatum, progenitors differentiated into striatal interneuron subtypes and were consistently found in the nearby septum and hippocampus. These findings highlight the potential for hPSC-derived striatal interneurons as an invaluable tool in modeling striatal development and function in vitro or as a source of cells for regenerative medicine